

h3 {
    text-align: center;
}

p {
    text-align: center;
    margin: 5px auto;
}

p.title {
    color: blue;
    font-weight: bold;
}

p.desc {
    font-family: 宋体;
}

.wrapper {
    width: 800px;
    border: 1px solid gray;
    margin: 25px auto;
}

.flex-container {
    /* 使被选中的元素成为弹性容器 */
    display: flex;
    /* 设置 弹性方向 、是否折行或折列 */
    flex-flow: column-reverse nowrap;
    height: 200px;
    border: 1px solid blue;
    margin: 15px;
}

.flex-item {
    flex-basis: 40px;
}

.flex-item:nth-child(2n) {
    background: #ffff00;
}

.flex-item:nth-child(2n+1) {
    background: #dfdfdf;
}

.first {
    /* 控制容器内的弹性项目在容器主轴方向的对其方式 */
    justify-content: flex-start;
}

.second {
    justify-content: center;
}

.third {
    justify-content: flex-end;
}

.fourth {
    justify-content: space-between;
}

.fifth {
    justify-content: space-evenly;
}

.sixth {
    justify-content: space-around;
}

.seventh {
    flex-flow: column-reverse wrap;
    justify-content: space-between;
    height: 199px;
}
